Adsorption-decomposition cooperative treatment system for dioxin in sludge incineration flue gas

Abstract

The invention relates to the technical field of solid waste treatment and air pollution control, in particular to an adsorption-decomposition cooperative treatment system for dioxin in sludge incineration flue gas. In the treatment system, the active coke is modified to obtain a modified active coke material which is of a three-level pore structure and is loaded with catalytic sites, the modified active coke material is filled into the adsorption unit to adsorb the dioxin in the sludge incineration flue gas, and then the dioxin after adsorption is subjected to catalytic decomposition, so that the dioxin in the sludge incineration flue gas is subjected to catalytic decomposition. And regenerating the modified active coke material subjected to catalytic decomposition, and then adsorbing again to complete the treatment process of dioxin. According to the treatment system, dioxin adsorption and decomposition are integrated, the removal efficiency of dioxin in flue gas reaches 99% or above, air pollution control and environment protection are facilitated, and meanwhile the modified active coke material is good in use stability, long in service life and low in use cost and has good application and popularization prospects.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment and air pollution control technology, specifically to a synergistic treatment system for dioxin adsorption-decomposition in sludge incineration flue gas. Background Technology

[0002] Dioxins are a class of highly toxic tricyclic aromatic organic compounds, including those with acute lethal toxicity and carcinogenicity. Dioxins are almost non-naturally occurring in nature, being byproducts of combustion and various industrial production processes. They possess extremely strong chemical and thermal stability, and once they infiltrate the environment, they are difficult to degrade and eliminate naturally, hence the nickname "poison of the century," posing a serious threat to health and environmental safety.

[0003] During the sludge reduction process, the flue gas from sludge incineration contains a small amount of dioxins, with a concentration of approximately 0.1–10 ng TEQ / m³. 3 Existing activated carbon spray adsorption methods require large activated carbon dosages, approximately 50–200 mg / m³. 3 In addition to being costly, it also generates hazardous waste, which is not easy to handle safely and further increases the cost of treatment; catalytic filtration (SCR / SNCR) requires high temperature (200-400℃) and the catalyst is prone to poisoning and failure.

[0004] Although activated carbon has adsorption and catalytic potential, existing activated carbon has a low adsorption capacity for dioxin molecules (approximately 1.2 nm in size) due to its microporous structure (<1 nm), and the activated carbon after adsorption also generates hazardous waste. Therefore, there are still considerable challenges in the treatment of dioxins. Thus, this invention develops a dioxin adsorption-decomposition synergistic treatment system based on modified activated carbon materials to achieve low-temperature and efficient removal of dioxins. At the same time, the modified activated carbon materials can be recycled, which facilitates resource conservation and environmental protection. Summary of the Invention

[0005] The purpose of this invention is to provide a synergistic treatment system for dioxin adsorption-decomposition in sludge incineration flue gas, in order to solve the problems of high cost of activated carbon adsorption of dioxins in existing sludge incineration flue gas, the generation of hazardous waste after activated carbon adsorption, which is not convenient for safe treatment and further increases the treatment cost.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a dioxin adsorption-decomposition synergistic treatment system in sludge incineration flue gas, comprising an adsorption unit, wherein the adsorption unit is filled with modified activated coke material;

[0007] The modified activated carbon material has a three-level pore structure of "micropore-mesopore-macropore", wherein the micropores account for 30-50%, the mesopores account for 40-60%, and the macropores account for 5-15%; and it is loaded with nano CeO2-TiO2 composite oxide catalytic sites.

[0008] The adsorption unit is configured in multiple ways, and each adsorption unit sequentially passes through an adsorption section, a catalytic decomposition section, and a regeneration section; the multiple adsorption units cooperate in a staggered manner to continuously treat the flue gas from sludge incineration.

[0009] Furthermore, in the aforementioned tertiary pore structure, micropores have a diameter < 2 nm, mesopores have a diameter ≥ 2 nm and ≤ 50 nm, and macropores have a diameter > 50 nm; the tertiary pore structure is obtained by activated carbon through activation regulation, and the activation adopts a combined chemical and physical activation method.

[0010] Furthermore, in the aforementioned chemical-physical combined activation method, the chemical activator includes KOH, and the physical activator includes CO2. The activated coke is pulverized, sieved, dried, and then thoroughly mixed with the chemical activator. It is then activated at high temperature under a protective atmosphere. After the chemical activation is completed, the physical activator is continuously introduced under high temperature conditions to complete the entire activation process. After activation, the activated coke is cooled, acid-washed, washed with water until neutral, and dried to obtain a three-dimensional porous activated coke material.

[0011] Further, the activated coke is pulverized and passed through a 100-200 mesh sieve; the mass ratio of chemical activator to activated coke is 1-5:1; the protective atmosphere includes nitrogen, argon, and helium; the activation temperature is 500-1000℃, and the chemical activation time is 1-4 hours; the flow rate of the protective atmosphere is 100-200 mL / min, the flow rate of the physical activator is 1-5 mL / min, and the amount of physical activator is 30-50 mL; the specific surface area of ​​the tertiary porous activated coke material is 500-800 m². 2 / g.

[0012] Furthermore, the catalytic sites of the nano-CeO2-TiO2 composite oxide are loaded onto a tertiary porous activated carbon material; the tertiary porous activated carbon material is added to a Ce and Ti salt solution, fully impregnated, filtered, and calcined to obtain the modified activated carbon material of the present invention.

[0013] Furthermore, the loading of the nano-CeO2-TiO2 composite oxide is 1-10%, and the particle size is 10-20 nm; the mass-to-volume ratio of the tertiary porous activated coke material to the salt solution is 1:5-15; in the salt solution, the Ce salt includes cerium nitrate, the Ti salt includes titanium sulfate, the total solute concentration is 1-10 g / L, the molar ratio of Ce to Ti is 1:1-3, the calcination temperature is 300-500℃, and the calcination time is 2-4 h.

[0014] Furthermore, in each of the aforementioned adsorption units, after the adsorption section of a certain adsorption unit is completed, the adsorption unit sequentially enters the catalytic decomposition section and the regeneration section. After the regeneration section is completed, the flue gas is reintroduced into the adsorption unit after the adsorption section of another adsorption unit has been completed, thus achieving continuous operation.

[0015] Furthermore, in the adsorption section, the flue gas velocity is 0.1–0.5 m / s, the flue gas contact time is 1–10 s, and the adsorption section duration is 7–15 days; in the catalytic decomposition section, the temperature is 80–150℃, and ultraviolet light irradiation is used with a wavelength of 200–300 nm and an intensity of 10–100 mW / cm². 2 The catalytic decomposition section lasts for 2–4 hours; the regeneration section is purged with low-pressure steam at 120–150°C, and the HCl in the regeneration tail gas is absorbed by alkaline solution. The regeneration section lasts for 2–4 hours.

[0016] Furthermore, each adsorption unit is divided into two groups: a primary adsorption unit group and a secondary adsorption unit group. The flue gas after the first adsorption in the primary adsorption unit group enters the secondary adsorption unit group for secondary adsorption. Each adsorption unit group cooperates with each other. The period of cooperation between each adsorption unit group in the secondary adsorption unit group is greater than or equal to the period of cooperation between each adsorption unit group in the primary adsorption unit group.

[0017] Furthermore, after adsorption and decomposition, the total removal rate of dioxins is greater than 99%, and the replacement cycle of the modified activated carbon material is not less than 2 years.

[0018] The beneficial effects of this invention are as follows: The processing system of this invention modifies activated carbon to obtain a modified activated carbon material with a modified tertiary porous structure and catalytic sites. This activated carbon material can achieve a dioxin removal rate of over 99% in flue gas, realizing in-situ adsorption and decomposition of dioxins, and enabling the recycling and utilization of the modified activated carbon material. This is of great significance for air pollution control and environmental protection, and has broad application and promotion prospects. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.

[0020] Example 1

[0021] Activated coke raw material was pulverized and passed through a 150-mesh sieve to obtain activated coke powder, which was then dried for later use. KOH was used as a chemical activator and mixed evenly with the activated coke powder at a mass ratio of 2:1. After uniform mixing, high-temperature chemical activation was performed under a nitrogen protective atmosphere. The nitrogen flow rate was 150 mL / min, the chemical activation temperature was 800℃, and the chemical activation time was 2 hours. After chemical activation, the temperature was kept constant while physical activation continued. The physical activator was CO2, with a CO2 flow rate of 3 mL / min and an injection volume of 40 mL. After the CO2 injection was completed, the physical activation process ended. The activated coke material was cooled, then acid-washed with hydrochloric acid, followed by water washing until neutral, filtering, and drying to obtain a three-dimensional porous activated coke material. The specific surface area of ​​this three-dimensional porous activated coke material was measured to be approximately 750 m² / g. 2 / g, of which the proportions of pore sizes are as follows: micropores (<2nm) 46.2%, mesopores (≥2nm, ≤50nm) 45.7%, and macropores (>50nm) 8.1%.

[0022] An 8 g / L cerium nitrate solution and a 10 g / L titanium sulfate solution were prepared and mixed in equal volumes to obtain a salt solution. The obtained tertiary porous activated carbon material was then thoroughly mixed with the salt solution at a mass-to-volume ratio of 1:10 (kg / L) for impregnation. After impregnation, the mixture was filtered and calcined at 450°C for 3 hours. After calcination, the material was cooled to obtain the modified activated carbon material of this invention. The CeO2-TiO2 composite oxide loading of the modified activated carbon material was found to be 6.8%, and the particle size was mainly distributed between 10 and 20 nm.

[0023] The modified activated carbon material was loaded into an adsorption tower unit to a height of 1 m. Two adsorption tower units were connected in parallel to treat the sludge incineration flue gas. The flue gas was monitored, and the temperature was 113℃, the oxygen content was 6.4%, and the average dioxin concentration was 8.5 ng TEQ / m³. 3 .

[0024] During the treatment process, the flow velocity inside the flue gas tower was 0.2 m / s. Testing showed that the average dioxin concentration in the flue gas at the outlet of the adsorption tower unit was 0.06 ng TEQ / m³. 3 The removal rate was 99.29%. After 10 days of operation, the two towers were switched. The adsorption tower unit, after adsorption was completed, entered the catalytic decomposition section. During this process, ultraviolet LED array irradiation was used with a wavelength of 254nm and an intensity of 50mW / cm². 2The temperature was 120℃ and the time was 3 hours. After the catalytic decomposition section was completed, the catalytic decomposition efficiency was 99.82% and the total removal efficiency was 99.12%. After the catalytic decomposition section was completed, the regeneration section was started. In the regeneration section, low-pressure steam at 120-150℃ was introduced into the adsorption tower unit to blow out the HCl, H2O and other substances generated in the catalytic decomposition section, and they were absorbed by alkaline solution. The regeneration section lasted for 4 hours, and then the unit entered an idle stage, waiting for the completion of another adsorption section before being reintroduced with flue gas.

[0025] To further improve removal efficiency, a two-stage adsorption method was adopted. The flue gas after primary adsorption was passed into the secondary adsorption tower unit for further adsorption. The operating parameters of the secondary adsorption tower unit were the same as those described above. Testing showed that the average dioxin concentration in the flue gas at the outlet of the secondary adsorption tower unit was 0.02 ng TEQ / m³. 3 The removal rate was 99.76%, the catalytic decomposition efficiency of the secondary adsorption tower unit was 99.92%, and the total removal rate was 99.41%. The dioxins in the flue gas outlet fully met the EU 2017 / 2272 ultra-low emission standard (<0.1 ng TEQ / m³). 3 Because the adsorption capacity of the secondary adsorption tower unit is relatively small, the actual regeneration cycle during operation is relatively long, which is 2 months.

[0026] After six months of actual operation, the system of this invention operated well without replacing the activated coke, and the dioxin concentration at the flue gas outlet did not fluctuate significantly. The expected service life of the activated coke is at least two years.

[0027] Under the same operating conditions, the activated carbon dosage of the treatment system of this invention is approximately 150 mg / m³ compared to traditional activated carbon spray adsorption. 3 In contrast, the dioxin removal rate is only about 95%, and about 300 kg / month of hazardous activated carbon ash is generated. Compared with this, the operating cost of this invention is reduced by about 60%.

[0028] This invention is not limited to the preferred embodiments described above. Anyone can derive other forms of products under the guidance of this invention. However, regardless of any changes made in their shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A synergistic treatment system for dioxin adsorption-decomposition in sludge incineration flue gas, characterized in that: Includes an adsorption unit, wherein the adsorption unit is filled with a modified activated char material; The modified activated carbon material has a three-level pore structure of "micropore-mesopore-macropore", wherein the micropores account for 30-50%, the mesopores account for 40-60%, and the macropores account for 5-15%; and it is loaded with nano CeO2-TiO2 composite oxide catalytic sites. The adsorption unit is configured in multiple ways, and each adsorption unit sequentially passes through an adsorption section, a catalytic decomposition section, and a regeneration section; the multiple adsorption units cooperate in a staggered manner to continuously treat the flue gas from sludge incineration.

2. The dioxin adsorption-decomposition synergistic treatment system for sludge incineration flue gas according to claim 1, characterized in that: The aforementioned tertiary pore structure was obtained by activation and regulation of activated coke, and the activation was carried out using a combined chemical and physical activation method.

3. The dioxin adsorption-decomposition synergistic treatment system for sludge incineration flue gas according to claim 2, characterized in that: In the aforementioned chemical-physical combined activation method, the chemical activator includes KOH, and the physical activator includes CO2. The activated coke is pulverized, sieved, dried, and then thoroughly mixed with the chemical activator. It is then activated at high temperature under a protective atmosphere. After the chemical activation is completed, the physical activator is continuously introduced under high temperature conditions to complete the entire activation process. After activation, the activated coke is cooled, acid-washed, washed with water until neutral, and dried to obtain a three-dimensional porous activated coke material.

4. The dioxin adsorption-decomposition synergistic treatment system for sludge incineration flue gas according to claim 3, characterized in that: The activated coke is pulverized and passed through a 100-200 mesh sieve; the mass ratio of chemical activator to activated coke is 1-5:1; the protective atmosphere includes nitrogen, argon, and helium; the activation temperature is 500-1000℃, and the chemical activation time is 1-4 hours; the flow rate of the protective atmosphere is 100-200 mL / min, the flow rate of the physical activator is 1-5 mL / min, and the amount of physical activator is 30-50 mL; the specific surface area of ​​the tertiary porous activated coke material is 500-800 m². 2 / g.

5. The dioxin adsorption-decomposition synergistic treatment system for sludge incineration flue gas according to claim 3, characterized in that: The catalytic sites of the nano-CeO2-TiO2 composite oxide are loaded onto a tertiary porous activated carbon material. The tertiary porous activated carbon material is added to a Ce and Ti salt solution, fully impregnated, filtered, and calcined to obtain the modified activated carbon material of the present invention.

6. The dioxin adsorption-decomposition synergistic treatment system for sludge incineration flue gas according to claim 5, characterized in that: The loading of the nano-CeO2-TiO2 composite oxide is 1-10%, and the particle size is 10-20 nm; the mass-to-volume ratio of the tertiary porous activated coke material to the salt solution is 1:5-15; in the salt solution, the Ce salt includes cerium nitrate, the Ti salt includes titanium sulfate, the total solute concentration is 1-10 g / L, the molar ratio of Ce to Ti is 1:1-3, the calcination temperature is 300-500℃, and the calcination time is 2-4 h.

7. The dioxin adsorption-decomposition synergistic treatment system for sludge incineration flue gas according to claim 1, characterized in that: In each of the aforementioned adsorption units, after the adsorption section of a certain adsorption unit is completed, the adsorption unit sequentially enters the catalytic decomposition section and the regeneration section. After the regeneration section is completed, the flue gas is reintroduced into the adsorption unit after the adsorption section of another adsorption unit has been completed, thus achieving continuous operation.

8. The dioxin adsorption-decomposition synergistic treatment system for sludge incineration flue gas according to claim 7, characterized in that: In the adsorption section, the flue gas velocity is 0.1–0.5 m / s, the flue gas contact time is 1–10 s, and the adsorption section duration is 7–15 days; in the catalytic decomposition section, the temperature is 80–150℃, and ultraviolet light irradiation is used with a wavelength of 200–300 nm and an intensity of 10–100 mW / cm². 2 The catalytic decomposition section lasts for 2–4 hours; the regeneration section is purged with low-pressure steam at 120–150°C, and the HCl in the regeneration tail gas is absorbed by alkaline solution. The regeneration section lasts for 2–4 hours.

9. The dioxin adsorption-decomposition synergistic treatment system for sludge incineration flue gas according to claim 7, characterized in that: Each adsorption unit is divided into two groups: a primary adsorption unit group and a secondary adsorption unit group. The flue gas after the first adsorption in the primary adsorption unit group enters the secondary adsorption unit group for secondary adsorption. Each adsorption unit group cooperates with each other. The period of cooperation between each adsorption unit group in the secondary adsorption unit group is greater than or equal to the period of cooperation between each adsorption unit group in the primary adsorption unit group.

10. The dioxin adsorption-decomposition synergistic treatment system for sludge incineration flue gas according to any one of claims 1-9, characterized in that: After adsorption and decomposition, the total removal rate of dioxins is greater than 99%, and the replacement cycle of the modified activated carbon material is not less than 2 years.